We never parsed/returned any data from .get_link() when the object is a windows reparse-point
containing a symlink. This results in the VFS layer oopsing accessing an uninitialized buffer:
...
[ 171.407172] Call Trace:
[ 171.408039] readlink_copy+0x29/0x70
[ 171.408872] vfs_readlink+0xc1/0x1f0
[ 171.409709] ? readlink_copy+0x70/0x70
[ 171.410565] ? simple_attr_release+0x30/0x30
[ 171.411446] ? getname_flags+0x105/0x2a0
[ 171.412231] do_readlinkat+0x1b7/0x1e0
[ 171.412938] ? __ia32_compat_sys_newfstat+0x30/0x30
...
Fix this by adding code to handle these buffers and make sure we do return a valid buffer
to .get_link()
CC: Stable <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Ronnie Sahlberg <lsahlber@xxxxxxxxxx>
---
fs/cifs/smb2ops.c | 64 +++++++++++++++++++++++++++++++++++++++++++++++++++----
fs/cifs/smb2pdu.h | 16 +++++++++++++-
2 files changed, 75 insertions(+), 5 deletions(-)
diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index e921e6511728..74c826007069 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -2385,6 +2385,41 @@ smb2_get_dfs_refer(const unsigned int xid, struct cifs_ses *ses,
kfree(dfs_rsp);
return rc;
}
+
+static int
+parse_reparse_symlink(struct reparse_symlink_data_buffer *symlink_buf,
+ u32 plen, char **target_path,
+ struct cifs_sb_info *cifs_sb)
+{
+ unsigned int sub_len;
+ unsigned int sub_offset;
+
+ /* We only handle Symbolic Link : MS-FSCC 2.1.2.4 */
+ if (le32_to_cpu(symlink_buf->ReparseTag) != REPARSE_TAG_SYMLINK) {
+ cifs_dbg(VFS, "srv returned invalid symlink buffer\n");
+ return -EIO;
+ }
+
+ sub_offset = le16_to_cpu(symlink_buf->SubstituteNameOffset);
+ sub_len = le16_to_cpu(symlink_buf->SubstituteNameLength);
+ if (sub_offset + 20 > plen ||
+ sub_offset + sub_len + 20 > plen) {
+ cifs_dbg(VFS, "srv returned malformed symlink buffer\n");
+ return -EIO;
+ }
+
+ *target_path = cifs_strndup_from_utf16(
+ symlink_buf->PathBuffer + sub_offset,
+ sub_len, true, cifs_sb->local_nls);
+ if (!(*target_path))
+ return -ENOMEM;
+
+ convert_delimiter(*target_path, '/');
+ cifs_dbg(FYI, "%s: target path: %s\n", __func__, *target_path);
+
+ return 0;
+}
+
#define SMB2_SYMLINK_STRUCT_SIZE \
(sizeof(struct smb2_err_rsp) - 1 + sizeof(struct smb2_symlink_err_rsp))
@@ -2414,11 +2449,13 @@ smb2_query_symlink(const unsigned int xid, struct cifs_tcon *tcon,
struct kvec close_iov[1];
struct smb2_create_rsp *create_rsp;
struct smb2_ioctl_rsp *ioctl_rsp;
- char *ioctl_buf;
+ struct reparse_data_buffer *reparse_buf;
u32 plen;
cifs_dbg(FYI, "%s: path: %s\n", __func__, full_path);
+ *target_path = NULL;
+
if (smb3_encryption_required(tcon))
flags |= CIFS_TRANSFORM_REQ;
@@ -2496,17 +2533,36 @@ smb2_query_symlink(const unsigned int xid, struct cifs_tcon *tcon,
if ((rc == 0) && (is_reparse_point)) {
/* See MS-FSCC 2.3.23 */
- ioctl_buf = (char *)ioctl_rsp + le32_to_cpu(ioctl_rsp->OutputOffset);
+ reparse_buf = (struct reparse_data_buffer *)
+ ((char *)ioctl_rsp +
+ le32_to_cpu(ioctl_rsp->OutputOffset));
plen = le32_to_cpu(ioctl_rsp->OutputCount);
if (plen + le32_to_cpu(ioctl_rsp->OutputOffset) >
rsp_iov[1].iov_len) {
- cifs_dbg(VFS, "srv returned invalid ioctl length: %d\n", plen);
+ cifs_dbg(VFS, "srv returned invalid ioctl len: %d\n",
+ plen);
+ rc = -EIO;
+ goto querty_exit;
+ }
+
+ if (plen < 8) {
+ cifs_dbg(VFS, "reparse buffer is too small. Must be "
+ "at least 8 bytes but was %d\n", plen);
+ rc = -EIO;
+ goto querty_exit;
+ }
+
+ if (plen < le16_to_cpu(reparse_buf->ReparseDataLength) + 8) {
+ cifs_dbg(VFS, "srv returned invalid reparse buf "
+ "length: %d\n", plen);
rc = -EIO;
goto querty_exit;
}
- /* Do stuff with ioctl_buf/plen */
+ rc = parse_reparse_symlink(
+ (struct reparse_symlink_data_buffer *)reparse_buf,
+ plen, target_path, cifs_sb);
goto querty_exit;
}
diff --git a/fs/cifs/smb2pdu.h b/fs/cifs/smb2pdu.h
index c7d5813bebd8..31f7c56e0ed8 100644
--- a/fs/cifs/smb2pdu.h
+++ b/fs/cifs/smb2pdu.h
@@ -888,6 +888,8 @@ struct file_allocated_range_buffer {
/* struct fsctl_reparse_info_req is empty, only response structs (see below) */
+#define REPARSE_TAG_SYMLINK 0xa000000c
+
struct reparse_data_buffer {
__le32 ReparseTag;
__le16 ReparseDataLength;
@@ -914,7 +916,19 @@ struct reparse_mount_point_data_buffer {
__u8 PathBuffer[0]; /* Variable Length */
} __packed;
-/* See MS-FSCC 2.1.2.4 and cifspdu.h for struct reparse_symlink_data */
+#define SYMLINK_FLAG_RELATIVE 0x00000001
+
+struct reparse_symlink_data_buffer {
+ __le32 ReparseTag;
+ __le16 ReparseDataLength;
+ __u16 Reserved;
+ __le16 SubstituteNameOffset;
+ __le16 SubstituteNameLength;
+ __le16 PrintNameOffset;
+ __le16 PrintNameLength;
+ __le32 Flags;
+ __u8 PathBuffer[0]; /* Variable Length */
+} __packed;
/* See MS-FSCC 2.1.2.6 and cifspdu.h for struct reparse_posix_data */
--
2.13.6
